A mortgage payment is calculated the same way as any amortizing loan — but the down payment matters a lot, since it directly determines how much you actually need to borrow.
What this doesn't include
This shows principal and interest only — real monthly housing costs usually also include property tax, homeowners insurance, and possibly private mortgage insurance (PMI) if your down payment is under 20%. Your actual payment will likely be higher than shown here.
Why the down payment percentage matters
A bigger down payment means a smaller loan, which means both a lower monthly payment and less total interest paid over the life of the loan — and above 20% down, you typically avoid PMI entirely.